With the ever increasing use and popularity of colour coded filing systems in offices there is a decided trend to the use of side tab folders. Side tab folders should be distinguished from top tab folders. Top tab folders are indexed on the upper edge parallel to the spine or fold between the front and back surfaces of the folder. Side tab folders are indexed on the side at right angles to the spine or fold. The file folders are placed upright on shelves with their side edges projecting outwardly from the shelf. Side tab filing systems have become most advantageous, especially in larger filing systems, because the filing and finding of folders is faster and easier. Also, side tab filing systems save floor space as compared with drawer filing. The colour coding of the files is not a necessity but can usually be an enhancement. The reinforced edge can advantageously be used in either top or lateral systems.
An example of side tab file systems is disclosed in U.S. Pat. No. 4,204,639. Usually file folders remain in a filing system for many years and during the life of the folder are subjected to considerable wear and tear and often to severe handling and abuse. Also, as they are moved between the file room to the user departments they are often roughly handled as they are temporarily placed in holding baskets or carts with the side tab projecting. This projecting tab is exposed and thus vulnerable to creasing, tearing and fatigue.
The folder stock commonly used for file folders, backers and the like is a folder stock approximately 0.011 inches or 0.014 inches thick. The folders are manufactured from web stock on high speed automatic folder machines.
In the past, many attempts have been made to reinforce file folder edges, especially the top tab type which have been commonly used for many years and are stored in file drawers. Usually the upper edge of the file folder is reinforced in one way or another to withstand abuse. An example of such file folder reinforcement is disclosed in U.S. Pat. No. 1,743,191. In that instance, the upper edge of the rear panel of the folder has an additional layer of file folder stock glued to the upper edge and wrapped aroung the upper edge of the folder to provide a three ply thickness to substantially reinforce the upper edge. Other examples of similar manners for reinforcing file folder edges, are disclosed in U.S. Pat. Nos. 1,081,727; 2,052,623 and 2,138,788. In each instance, either the file folder stock integral with the folder is folded over and glued to reinforce the edge or additional material is added of the same file folder stock to reinforce the edge.
The approach to date has, therefore, been to add additional layers of the folder stock to the folder edge in an attempt to reinforce and add stiffness to the folder edge to resist tearing.
Various forms of high tensile strength films have been used to repair rips in paper and protect surfaces of paper products. An example of such film is Mylar (trademark) which consists of polyethylene terephthalate and is sold by Du Pont. In the file folder field, such film is used to protect add-on file folder tabs as disclosed in copending U.S. patent Ser. No. 276,939 which corresponds to Canadian Patent application Ser. No. 380,208 filed June 19, 1981.
It has been discovered as discussed below that this type of high tensile strength film may be bonded to the edge of a file folder to unexpectedly greater increase the strength of the folder and its resistance to tear. Because of the thinness of the film, little bulk is added to the folder thickness and the film may be conveniently applied during the manufacture of the file folder. By using coloured adhesives, which may be applied to a clear film just prior to bonding the film to the folder edge, the edge of the folder front and back panels may be provided with a distinct colour to which colour coded labels may be subsequently applied. An alternative to a coloured adhesive is to use a coloured paper on the folder edge which is covered by a clear film. Another alternative is to use coloured film which is secured to the folder edge to provide the desired colour band. This is a significant advantage in that groups of files of a file system may now be recognized by the complete band of colour down its front and back panel edges. This avoids the prior more costly approach of using many different coloured folder stocks for distinguishing each desired group of files in the system. Such coloured paper stock would fade and loose its distinctive colour. In addition, the colour of the folder stock would change from batch to batch of the stock, so that there would not be a consistent colouring for a group of files.
The folders can be manufactured from web stock on high speed automatic folder machines where the high tensile strength film when bonded to the edge of a file folder unexpectedly greatly increases the strength of the folder and its resistance to tear. This advantage can be accomplished during the folder manufacturing process in a way that only marginally increases the manufacturing cost. This marginal cost factor in relation to a much superior file folder is a worthwhile and important advantage. Such high tensile strength film compliments and increases additionally the strength of a folder edge which consists of ploughed over web stock to provide a double thickness of paper stock at the edge. Also, the high tensile strength film provides a superior bonding surface for the attachment of the self adhesive indexing and colour coded labels used to identify the folders.